It is well known that the controlled release of fertilizer has many advantages. The controlled release of fertilizer prevents "burning." The controlled release fertilizer is also less likely to be washed away. Additionally, more convenient applications are facilitated with a controlled, either slow or limited, release fertilizer due to the need for less frequent and critical applications.
There have been different approaches to providing a controlled release fertilizer. The placement of a coating on the fertilizer is one such solution. Various coatings have been used, such as those disclosed in U.S. Pat. No. 4,549,897 issuing to Seng et al on Oct. 29, 1985 and entitled "Protein Degraded Pre-Vulcanized Natural Rubber Coated Slow Release Fertilizers", and U.S. Pat. No. 4,880,455 issuing to Blank on Nov. 14, 1989 and entitled "Method for the Manufacture of Slow Release Fertilizers". Yet another approach is to provide substances that act as a fertilizer that have relatively low levels of solubility. One example of such a fertilizer is disclosed in U.S. Pat. No. 3,574,591 issuing to Lyons et al on Apr. 13, 1971 and entitled "Methods for Preparing Mixed Cation Polyphosphates". Therein disclosed is a fertilizer composition of mixed cation polyphosphates with reduced solubility.
There is a need for an easily prepared complete fertilizer that has controlled release due to low solubility.